Water-blocking-removing agent for water-containing gas well of tight sandstone reservoir as well as preparation method and application of water-blocking-removing agent

Abstract

The invention discloses a tight sandstone reservoir water-containing gas well water block removing agent and a preparation method and application, belongs to the technical field of gas reservoir development, and is characterized in that the water block removing agent comprises the following components in parts by weight: 20-35 parts of an ampholytic surfactant, 0.3-0.5 part of a fluorocarbon surfactant, 5-10 parts of a wetting agent, 5-10 parts of a solvent and 30-45 parts of water. The prepared water block removing agent is easy to biodegrade and low in surface tension and interfacial tension, the wettability of a rock core can be gradually changed from hydrophilic to hydrophobic, the rock wettability is effectively changed, the interfacial tension between fluid and reservoir rock is reduced, the permeability of the rock core is improved, and then the single-well recovery efficiency of a tight sandstone gas reservoir water-containing gas well is improved.

Description

Technical Field

[0001] This invention relates to the field of gas reservoir development technology, and in particular to a water-locking agent for water-bearing gas wells in tight sandstone reservoirs, its preparation method, and its application. Background Technology

[0002] Due to its low porosity, low permeability, high water saturation, severe heterogeneity, and high water sensitivity, the Sulige gas field faces significant challenges as formation fluids enter and create strong capillary resistance. This causes water to accumulate at the pore throats of the matrix, forming bound water and reducing the relative permeability of the gas phase. As formation energy decays and pressure decreases, it becomes insufficient to overcome the capillary resistance of the liquid phase, leading to a sharp decline in porosity and permeability. This can easily result in liquid phase trapping, causing water-locking damage, affecting single-well productivity, and significantly reducing gas well recovery.

[0003] Chinese patent document CN113429956A, published on September 24, 2021, discloses a hydro-locking agent, its preparation method, and its application. The hydro-locking agent comprises: a nano-active agent material, anionic surfactant, anionic-nonionic surfactant, cationic surfactant, solubilizer, and water. The nano-active agent material is obtained by polymerizing a layered nanomaterial containing double bond modification, a hydrophilic monomer, and a hydrophobic monomer. The hydrophilic monomer is selected from at least one of acid anhydride compounds. The hydrophobic monomer is selected from at least one of long-chain alkyl allyl quaternary ammonium salts.

[0004] The patent document discloses a water-locking agent, its preparation method, and its application. The water-locking agent has the characteristics of good high temperature resistance and salt resistance, low dosage, and convenient use.

[0005] Chinese patent document CN114479808A, published on May 13, 2022, discloses a water-locking agent for natural gas reservoirs, its preparation method, and its application. The water-locking agent, based on 100% of its total mass, may contain the following components by mass percentage: A. fluorocarbon surfactant, 5%–20%; B. biosurfactant, 5%–20%; C. synergist, 5%–30%; D. water, 30%–85%. This water-locking agent can significantly reduce the surface tension of water, regulating a strongly wetted matrix surface to neutral wetting or even hydrophobic, while simultaneously reducing the viscosity of the fluid.

[0006] The patent document discloses a water-locking agent for natural gas reservoirs, its preparation method, and its application, which can achieve the effect of relieving water-locking damage in natural gas reservoirs.

[0007] The existing technologies represented by the aforementioned patent documents produce water-locking agents that are not easily biodegradable and have poor surface tension and interfacial tension, which is not conducive to improving the single-well recovery rate. Summary of the Invention

[0008] To overcome the shortcomings of the prior art, this invention provides a water-locking agent for water-bearing gas wells in tight sandstone reservoirs, its preparation method, and its application. The water-locking agent prepared by this invention is easily biodegradable and has low surface tension and interfacial tension. It can gradually change the wettability of the core from hydrophilic to hydrophobic, effectively altering the rock wettability, reducing the interfacial tension between the fluid and the reservoir rock, and improving the core permeability, thereby improving the single-well recovery rate of water-bearing gas wells in tight sandstone gas reservoirs.

[0009] This invention is achieved through the following technical solution:

[0010] A water-locking agent for water-bearing gas wells in tight sandstone reservoirs, characterized in that it comprises the following components in parts by weight:

[0011] 20-35 parts of amphoteric surfactant

[0012] 0.3-0.5 parts of fluorocarbon surfactant

[0013] 5-10 parts wetting agent

[0014] 5-10 parts solvent

[0015] 30-45 parts water.

[0016] The amphoteric surfactant is a mixture of lauramidopropyl betaine and dodecyl dimethyl betaine.

[0017] The wetting agent is sodium dodecyl sulfate, sodium lauryl sulfate, or sodium alkylbenzene sulfonate.

[0018] The solvent is isopropanol or ethanol.

[0019] The fluorocarbon surfactant is FC-170C or FS-3100.

[0020] A method for preparing a water-locking agent for water-bearing gas wells in tight sandstone reservoirs, characterized by comprising the following steps:

[0021] Step S1: Add the amphoteric surfactant to water according to the formula amount, and stop stirring after the solution is evenly mixed to obtain amphoteric surfactant solution I;

[0022] Step S2: Add the fluorocarbon surfactant to the water according to the formula amount, and stop stirring after the solution is uniform to obtain fluorocarbon surfactant solution II;

[0023] Step S3: Mix the amphoteric surfactant solution I and the fluorocarbon surfactant solution II, then add the solvent of the formula amount, and stir at 200-400 rpm for 5-10 minutes. Stop stirring after the solution is uniform to obtain mixture III.

[0024] Step S4: After adding the prescribed amount of wetting agent to mixture III, stir the solution until it is homogeneous and then stop to obtain the water-locking agent.

[0025] In step S1, the stirring speed is 400-1000 rpm and the stirring time is 10-20 min.

[0026] In step S2, the stirring speed is 400-1000 rpm and the stirring time is 10-20 min.

[0027] In step S4, the stirring speed is 200-400 rpm and the stirring time is 20 min.

[0028] An application of a water-locking agent for water-bearing gas wells in tight sandstone reservoirs, characterized in that it is suitable for water-locking in tight sandstone gas reservoir development.

[0029] The reservoir dewatering process specifically refers to diluting the dewatering agent with water to an effective concentration of 0.01% to 10 w.t% before injecting it into the natural gas well.

[0030] The water-locking principle of the water-locking agent of this invention is as follows:

[0031] The water-locking agent is an organic combination of amphoteric surfactants, fluorocarbon surfactants, and wetting agents. Among them, amphoteric surfactants and fluorocarbon surfactants have a good synergistic effect. In the compound system, due to the interaction of positive and negative charges, the amphoteric surfactants and fluorocarbon surfactants are promoted to form adhesiodes. Due to the tighter intermolecular bonding, mixed micelles are formed, which reduces the oriented water molecules on the surface of the surfactant, and significantly improves the surface tension and interfacial tension performance. The addition of fluorocarbon surfactants can regulate the strongly wetted surface to neutral wetting, while reducing the fluid viscosity, thereby promoting the discharge of blockage water in the formation and playing a good role in de-watering.

[0032] The beneficial effects of this invention are mainly reflected in the following aspects:

[0033] 1. This invention uses a water-locking agent prepared with a specific composition and ratio of "20-35 parts of amphoteric surfactant, 0.3-0.5 parts of fluorocarbon surfactant, 5-10 parts of wetting agent, 5-10 parts of solvent, and 30-45 parts of water". Compared with the prior art, it is easier to biodegrade and has low surface tension and interfacial tension. It can reduce the surface tension to 11.6 mN / m and the interfacial tension to 0.06 mN / m. See Tables 1 and 2 in the specific examples. It can gradually change the wettability of the core from hydrophilic to hydrophobic, effectively change the wettability of the rock, reduce the interfacial tension between the fluid and the reservoir rock, improve the core permeability, and thus help improve the single-well recovery rate of water-bearing gas wells in tight sandstone gas reservoirs.

[0034] 2. In this invention, the amphoteric surfactant is a mixture of lauramidopropyl betaine and dodecyl dimethyl betaine, which can effectively reduce the interfacial tension between oil and water and reverse wetting. The amphoteric surfactant is adsorbed by underground rocks in tight sandstone reservoirs and forms a molecular film on the surface, thereby changing the interfacial tension of the underground system or causing the system to reverse wetting. At the same time, lauramidopropyl betaine and dodecyl dimethyl betaine have good compatibility with various types of surfactants and additives and have excellent synergistic effects.

[0035] 3. In this invention, the fluorocarbon surfactant is FC-170C or FS-3100. Fluorocarbon surfactants have extremely high surface activity and excellent stability. When combined with amphoteric surfactants, they can regulate the formation wetting properties in tight sandstone reservoirs by being reasonably adsorbed by underground rocks. Compared with general types of surfactants, they have a stronger ability to regulate wetting properties.

[0036] 4. In this invention, the wetting agent is sodium dodecyl sulfate, sodium lauryl sulfate, or sodium alkylbenzene sulfonate, which can improve the fluidity of the system and enable amphoteric surfactants and fluorocarbon surfactants to better adhere to the surface of the formation rock.

[0037] 5. The water-locking agent prepared by the method of this invention can reduce the interfacial tension of reservoir fluids to 0.08 mN / m. See [link to relevant documentation]. Figure 1 .

[0038] 6. According to the present invention, the permeability of the core can be restored to up to 93.86% of the original value after being displaced by the water-locking agent. See the experimental data in Table 3 of the specific examples.

[0039] 7. The water-lock removal agent prepared by this invention was used in 121 wells in the Sulige Gas Field area in 2023, with 99 wells showing effectiveness and 22 wells showing no effect. The effectiveness rate of the water-lock removal process was 81.8%, the average effective production days of the effective wells was 218 days, and the cumulative increase in natural gas production was 7890 × 10⁻⁶. 4 m 3 Effective wells increased daily natural gas production by more than 0.3 × 10⁻⁶. 4 m 3 The field application has yielded significant results, greatly improving the single-well recovery rate, as shown in Table 4 of the specific examples.

[0040] 8. The water-locking agent of this invention has strong temperature and salt resistance, good surface activity, low oil-water interfacial tension, and the wettability of the core gradually changes from hydrophilic to hydrophobic, increasing the contact angle by about 10°. After injecting the water-locking agent, the permeability recovery rate can be improved.

[0041] 9. In this invention, because the amount of fluorocarbon surfactant used is small, the use process will not cause pollution to the environment, and the entire preparation and production process of the water-locking agent is non-toxic and pollution-free.

[0042] 10. The water-locking agent prepared by this invention has strong permeability, can form an ultra-low interfacial tension, and can form stable and abundant low-density foam. In gas wells with severe water lock, it can efficiently penetrate into the reservoir pores, thereby displacing the accumulated fluid and achieving the purpose of relieving water lock.

[0043] 11. When applied to water-bearing gas wells in tight sandstone gas reservoirs, this invention can achieve the effects of increasing and stabilizing production. Attached Figure Description

[0044] The present invention will now be further described in detail with reference to the accompanying drawings and specific embodiments:

[0045] Figure 1 This is a schematic diagram of the final imaging of the hydrolytic interfacial tension meter experiment using the hydrolytic agent of the present invention. Detailed Implementation

[0046] Example 1

[0047] A water-locking agent for water-bearing gas wells in tight sandstone reservoirs, comprising the following components in parts by weight:

[0048] 20 parts of amphoteric surfactant

[0049] 0.3 parts of fluorocarbon surfactant

[0050] 5 parts wetting agent

[0051] 5 parts solvent

[0052] 30 parts water.

[0053] The amphoteric surfactant is a mixture of lauramidopropyl betaine and dodecyl dimethyl betaine.

[0054] The wetting agent is sodium dodecyl sulfate.

[0055] The solvent is isopropanol.

[0056] Example 2

[0057] A water-locking agent for water-bearing gas wells in tight sandstone reservoirs, comprising the following components in parts by weight:

[0058] 25 parts of amphoteric surfactant

[0059] 0.4 parts of fluorocarbon surfactant

[0060] 8 parts wetting agent

[0061] 8 parts solvent

[0062] 40 parts water.

[0063] The amphoteric surfactant is a mixture of lauramidopropyl betaine and dodecyl dimethyl betaine.

[0064] The wetting agent is sodium lauryl sulfate.

[0065] The solvent is isopropanol.

[0066] Example 3

[0067] A water-locking agent for water-bearing gas wells in tight sandstone reservoirs, characterized in that it comprises the following components in parts by weight:

[0068] 35 parts of amphoteric surfactant

[0069] 0.5 parts of fluorocarbon surfactant

[0070] 10 parts wetting agent

[0071] 10 parts of solvent

[0072] 45 parts water.

[0073] The amphoteric surfactant is a mixture of lauramidopropyl betaine and dodecyl dimethyl betaine.

[0074] The wetting agent is sodium alkylbenzene sulfonate.

[0075] The solvent is ethanol.

[0076] Example 4

[0077] A method for preparing a water-locking agent for water-bearing gas wells in tight sandstone reservoirs includes the following steps:

[0078] Step S1: Add the amphoteric surfactant to water according to the formula amount, and stop stirring after the solution is evenly mixed to obtain amphoteric surfactant solution I;

[0079] Step S2: Add the fluorocarbon surfactant to the water according to the formula amount, and stop stirring after the solution is uniform to obtain fluorocarbon surfactant solution II;

[0080] Step S3: Mix the amphoteric surfactant solution I and the fluorocarbon surfactant solution II, then add the solvent of the formula amount, and stir at 200 rpm for 5 minutes. Stop stirring after the solution is uniform to obtain mixture III.

[0081] Step S4: After adding the prescribed amount of wetting agent to mixture III, stir the solution until it is homogeneous and then stop to obtain the water-locking agent.

[0082] In step S1, the stirring speed is 400 rpm and the stirring time is 10 min.

[0083] In step S2, the stirring speed is 400 rpm and the stirring time is 10 min.

[0084] In step S4, the stirring speed is 200 rpm and the stirring time is 20 min.

[0085] The amphoteric surfactant is a mixture of lauramidopropyl betaine and dodecyl dimethyl betaine, which can effectively reduce the interfacial tension between oil and water and reverse wetting. In tight sandstone reservoirs, the amphoteric surfactant is adsorbed by underground rocks and forms a molecular film on the surface, thereby changing the interfacial tension of the underground system or causing wetting reversal. At the same time, lauramidopropyl betaine and dodecyl dimethyl betaine have good compatibility with various types of surfactants and additives and have excellent synergistic effects.

[0086] Example 5

[0087] A method for preparing a water-locking agent for water-bearing gas wells in tight sandstone reservoirs includes the following steps:

[0088] Step S1: Add the amphoteric surfactant to water according to the formula amount, and stop stirring after the solution is evenly mixed to obtain amphoteric surfactant solution I;

[0089] Step S2: Add the fluorocarbon surfactant to the water according to the formula amount, and stop stirring after the solution is uniform to obtain fluorocarbon surfactant solution II;

[0090] Step S3: Mix the amphoteric surfactant solution I and the fluorocarbon surfactant solution II, then add the amount of solvent specified in the formula, and stir at 300 rpm for 8 minutes. Stop stirring after the solution is homogeneous to obtain mixture III.

[0091] Step S4: After adding the prescribed amount of wetting agent to mixture III, stir the solution until it is homogeneous and then stop to obtain the water-locking agent.

[0092] In step S1, the stirring speed is 700 rpm and the stirring time is 15 min.

[0093] In step S2, the stirring speed is 800 rpm and the stirring time is 15 min.

[0094] In step S4, the stirring speed is 300 rpm and the stirring time is 20 min.

[0095] Example 6

[0096] A method for preparing a water-locking agent for water-bearing gas wells in tight sandstone reservoirs includes the following steps:

[0097] Step S1: Add the amphoteric surfactant to water according to the formula amount, and stop stirring after the solution is evenly mixed to obtain amphoteric surfactant solution I;

[0098] Step S2: Add the fluorocarbon surfactant to the water according to the formula amount, and stop stirring after the solution is uniform to obtain fluorocarbon surfactant solution II;

[0099] Step S3: Mix the amphoteric surfactant solution I and the fluorocarbon surfactant solution II, then add the solvent of the formula amount, and stir at 400 rpm for 10 minutes. Stop stirring after the solution is uniform to obtain mixture III.

[0100] Step S4: After adding the prescribed amount of wetting agent to mixture III, stir the solution until it is homogeneous and then stop to obtain the water-locking agent.

[0101] In step S1, the stirring speed is 1000 rpm and the stirring time is 20 min.

[0102] In step S2, the stirring speed is 1000 rpm and the stirring time is 20 min.

[0103] In step S4, the stirring speed is 400 rpm and the stirring time is 20 min.

[0104] The wetting agent is sodium dodecyl sulfate, sodium lauryl sulfate, or sodium alkylbenzene sulfonate, which can improve the fluidity of the system and enable amphoteric surfactants and fluorocarbon surfactants to better adhere to the surface of the formation rocks.

[0105] Example 7

[0106] An application of a water-locking agent for water-bearing gas wells in tight sandstone reservoirs, applicable to water-locking in tight sandstone gas reservoir development.

[0107] The reservoir dewatering process specifically refers to diluting the dewatering agent with water to an effective concentration of 0.01% before injecting it into the natural gas well.

[0108] Example 8

[0109] An application of a water-locking agent for water-bearing gas wells in tight sandstone reservoirs, applicable to water-locking in tight sandstone gas reservoir development.

[0110] The reservoir dewatering process specifically refers to diluting the dewatering agent with water to an effective concentration of 10 w.t% before injecting it into the natural gas well.

[0111] The invention will now be illustrated with specific examples:

[0112] Specific Example 1

[0113] The weight percentages of each raw material are as follows: lauramidopropyl betaine: 20%; FC-170C: 0.5%; sodium dodecyl sulfate: 5%; ethanol: 5%; the remaining 69.5% is deionized water;

[0114] Preparation method: (1) Add the lauramidopropyl betaine to deionized water and stir at 800 rpm for 15 min. Stop stirring after ensuring the solution is uniform to obtain solution I of lauramidopropyl betaine; (2) Add the FC-170C agent to deionized water and stir at 800 rpm for 15 min. Stop stirring after ensuring the solution is uniform to obtain solution II of FC-170C; (3) Mix solution I of lauramidopropyl betaine and solution II of FC-170C and add ethanol. Stir at 300 rpm for 8 min. Stop stirring after ensuring the solution is uniform to obtain mixture III; (4) Add sodium dodecyl sulfate to mixture III and stir at 300 rpm for 20 min. Stop stirring after ensuring the solution is uniform to obtain dehydrating agent.

[0115] Specific Example 2

[0116] The weight percentages of each raw material are as follows: lauramidopropyl betaine: 30%; FC-170C: 0.75%; sodium dodecyl sulfate: 7.5%; ethanol: 7.5%; the remaining 54.25% is deionized water; the preparation method is the same as in specific example 1.

[0117] Specific Example 3

[0118] The weight percentages of each raw material are as follows: lauramidopropyl betaine: 40%; FC-170C: 1%; sodium dodecyl sulfate: 10%; ethanol: 10%; the remaining 49% is deionized water; the preparation method is the same as in specific example 1.

[0119] Specific Example 4

[0120] The weight percentages of each raw material are as follows: dodecyl dimethyl betaine: 20%; FS-3100: 0.5%; sodium lauryl sulfate: 5%; ethanol: 5%; the remaining 69.5% is deionized water;

[0121] Preparation method: (1) Add the dodecyl dimethyl betaine to deionized water and stir at 800 rpm for 15 min. Stop stirring after ensuring the solution is uniform to obtain solution I of dodecyl dimethyl betaine; (2) Add the FS-3100 agent to deionized water and stir at 800 rpm for 15 min. Stop stirring after ensuring the solution is uniform to obtain solution II of FS-3100; (3) Mix solution I of dodecyl dimethyl betaine and solution II of FS-3100 and add ethanol. Stir at 300 rpm for 8 min. Stop stirring after ensuring the solution is uniform to obtain mixture III; (4) Add sodium lauryl sulfate to mixture III and stir at 300 rpm for 20 min. Stop stirring after ensuring the solution is uniform to obtain water-locking agent.

[0122] Specific Example 5

[0123] The weight percentages of each raw material are as follows: dodecyl dimethyl betaine: 30%; FS-3100: 0.75%; sodium lauryl sulfate: 7.5%; ethanol: 7.5%; the remaining 54.25% is deionized water; the preparation method is the same as in specific example 4.

[0124] Specific Example 6

[0125] The weight percentages of each raw material are as follows: dodecyl dimethyl betaine: 40%; FS-3100: 0.1%; sodium lauryl sulfate: 10%; ethanol: 10%; the remaining 49% is deionized water; the preparation method is the same as in specific example 4.

[0126] Specific Example 7

[0127] The weight percentages of each raw material are as follows: dodecyl dimethyl betaine: 40.1%; sodium lauryl sulfate: 10%; ethanol: 10%; the remaining 49% is deionized water;

[0128] Preparation method: (1) Add the dodecyl dimethyl betaine to deionized water and stir at 800 rpm for 15 min. Stop stirring after ensuring the solution is uniform to obtain solution I of dodecyl dimethyl betaine; (2) Add ethanol to solution I containing dodecyl dimethyl betaine and stir at 300 rpm for 8 min. Stop stirring after ensuring the solution is uniform to obtain mixture III; (3) Add sodium lauryl sulfate to mixture III and stir at 300 rpm for 20 min. Stop stirring after ensuring the solution is uniform to obtain the water-locking agent.

[0129] Specific Example 8

[0130] The weight percentages of each raw material are as follows: dodecyl dimethyl betaine: 50%; FS-3100: 0.1%; ethanol: 10%; the remaining 49% is deionized water;

[0131] Preparation method: (1) Add the dodecyl dimethyl betaine to deionized water and stir at 800 rpm for 15 min. Stop stirring after ensuring the solution is uniform to obtain solution I of dodecyl dimethyl betaine; (2) Add the FS-3100 agent to deionized water and stir at 800 rpm for 15 min. Stop stirring after ensuring the solution is uniform to obtain solution II of FS-3100; (3) Mix solution I of dodecyl dimethyl betaine and solution II of FS-3100 and add ethanol. Stir at 300 rpm for 8 min. Stop stirring after ensuring the solution is uniform to obtain the water-locking agent.

[0132] The hydrolytic lock-in agents prepared in the above specific examples 1-8 were diluted with deionized water to an effective concentration of 0.5 wt%. The test method was in accordance with GB / T 22237-2008 Determination of surface tension of surfactants. The surface tension results are shown in Table 1.

[0133] Table 1

[0134]

[0135]

[0136] The dehydrating agents prepared in the above specific examples 1-8 were diluted to an effective concentration of 0.5 wt%, and their interfacial tension with kerosene was tested using a TX500 rotating drop interfacial tensiometer. The results are shown in Table 2.

[0137] Table 2

[0138] Specific examples Interfacial tension (mN / m) 1 0.10 2 0.12 3 0.08 4 0.11 5 0.06 6 0.06 7 0.26 8 0.16

[0139] The lower the surface tension and interfacial tension, the easier it is for the fluid that causes waterlocking to be removed from the capillary channels that cause the damage. The more hydrophobic the formation wettability, that is, the larger the contact angle between water and the matrix, the less likely water is to adhere to the surface of the formation matrix; the lower the fluid viscosity, the better the fluid flow and the easier it is to move in the formation, so that the fluid that causes waterlocking damage can be discharged as quickly as possible.

[0140] The test process for the permeability recovery rate of the water-locking agent of this invention is as follows:

[0141] The permeability recovery rate test was conducted using the dewatering agent configured in Specific Example 3. The implementation steps were as follows: (1) Take a low-permeability core with a gas permeability of 3.3 mD, a core diameter of 2.5 cm, and a core length of 3.0 cm. Dry the core at 60°C for later use. (2) Vacuum saturate the core with colorless kerosene. (3) Place the saturated core into the core flow path, heat it to 60°C, and equilibrate for 1 hour. Then, pass colorless kerosene in the forward direction at a flow rate of 0.2 mL / min until the core flow pressure and permeability stabilize at 0.5 h. (4) Then, pass 2% KCl brine in the reverse direction at a flow rate of 0.2 mL / min for 20 hours. (5) Then, pass colorless kerosene in the forward direction at a flow rate of 0.2 mL / min until the core flow pressure and permeability are stable for 0.5 h. Record the permeability value K1. (6) Dilute the water-locking agent 300 times with 2% KCl saline solution and pass the treatment agent 20PV in the reverse direction at a flow rate of 0.2 mL / min. The permeability value K2 is recorded. The formula for calculating the permeability recovery rate is: S=(K2-K1) / K1×100%.

[0142] Table 3 below shows the experimental data on the permeability recovery rate of core samples after displacement by the water-locking agent.

[0143] Table 3

[0144]

[0145] Table 4 below shows the water lock removal effect of gas wells in 2023.

[0146] Table 4

[0147]

[0148]

[0149]

[0150]

[0151] Water-lock removal agents were used in 121 wells in the Sulige gas field area in 2023, with 99 wells showing effectiveness and 22 wells showing no effect. The effectiveness rate of the water-lock removal measures was 81.8%, and the average effective production days of the effective wells was 218 days, resulting in a cumulative increase in natural gas production of 7890 × 10⁻⁶. 4 m 3 Effective wells increased daily natural gas production by more than 0.3 × 10⁻⁶. 4 m 3 The field application has yielded significant results, greatly improving the single-well recovery rate.

Claims

1. A water-locking agent for water-bearing gas wells in tight sandstone reservoirs, characterized in that: The components include the following parts by weight: 20-35 parts of amphoteric surfactant 0.3-0.5 parts of fluorocarbon surfactant 5-10 parts wetting agent 5-10 parts solvent 30-45 parts water.

2. The water-locking agent for water-bearing gas wells in tight sandstone reservoirs according to claim 1, characterized in that: The amphoteric surfactant is a mixture of lauramidopropyl betaine and dodecyl dimethyl betaine.

3. The water-locking agent for water-bearing gas wells in tight sandstone reservoirs according to claim 1, characterized in that: The wetting agent is sodium dodecyl sulfate, sodium lauryl sulfate, or sodium alkylbenzene sulfonate.

4. The water-locking agent for water-bearing gas wells in tight sandstone reservoirs according to claim 1, characterized in that: The solvent is isopropanol or ethanol.

5. The preparation method of a water-locking agent for a water-bearing gas well in a tight sandstone reservoir according to claim 1, characterized in that, Includes the following steps: Step S1: Add the amphoteric surfactant to water according to the formula amount, and stop stirring after the solution is evenly mixed to obtain amphoteric surfactant solution I; Step S2: Add the fluorocarbon surfactant to the water according to the formula amount, and stop stirring after the solution is uniform to obtain fluorocarbon surfactant solution II; Step S3: Mix the amphoteric surfactant solution I and the fluorocarbon surfactant solution II, then add the solvent of the formula amount, and stir at 200-400 rpm for 5-10 minutes. Stop stirring after the solution is uniform to obtain mixture III. Step S4: After adding the prescribed amount of wetting agent to mixture III, stir the solution until it is homogeneous and then stop to obtain the water-locking agent.

6. The method for preparing a water-locking agent for a water-bearing gas well in a tight sandstone reservoir according to claim 5, characterized in that: In step S1, the stirring speed is 400-1000 rpm and the stirring time is 10-20 min.

7. The method for preparing a water-locking agent for a water-bearing gas well in a tight sandstone reservoir according to claim 5, characterized in that: In step S2, the stirring speed is 400-1000 rpm and the stirring time is 10-20 min.

8. The method for preparing a water-locking agent for a water-bearing gas well in a tight sandstone reservoir according to claim 5, characterized in that: In step S4, the stirring speed is 200-400 rpm and the stirring time is 20 min.

9. The application of the water-locking agent for water-bearing gas wells in tight sandstone reservoirs according to claim 1, characterized in that: It is applicable to reservoir water-locking in the development of tight sandstone gas reservoirs.

10. The application of the water-locking agent for water-bearing gas wells in tight sandstone reservoirs according to claim 9, characterized in that: The reservoir dewatering process specifically refers to diluting the dewatering agent with water to an effective concentration of 0.01% to 10 w.t% before injecting it into the natural gas well.

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